In recent years, digital maps are widely used for cars, ships and air planes to check a location. Digital maps, which are utilized in various application systems based on a geographical information system (GIS), construct three-dimensional (3D) terrain via processing of digital map data stored in a storage device through a computer and represent the terrain via a display apparatus.
Digital maps are rendered by terrain modeling, wherein a digital elevation model (DEM) or contour line model is available. A DEM represents digital terrain via interpolation between height values (elevations) at grid points at regular intervals. A digital contour line model represents terrain through interpolation between contour lines.
A digital contour line model has a remarkably small data size as compared with a DEM but is not precise. A DEM is obtained by reading aerial photographs or satellite images and provide data with various resolutions based on an interval between grid points. Precision of terrain is determined on an interval between grid points and thus ultimately depends on a resolution of a DEM. High-resolution terrain data is precise but needs a substantially great data size, whereas low-resolution terrain data is not precise but needs a small data size.
Active use of high-resolution terrain data of digital maps is difficult due to limitation on computer resources available to provide terrain. In particular, only limited computer resources are allowed to be mounted in transportations frequently using digital maps, such as a car, ship and air plane, making it difficult to manage high-capacity data.